TY - JOUR
T1 - The impact of biostimulation on the fate of sulfate and associated sulfur dynamics in groundwater
AU - Miao, Ziheng
AU - Carreón-Diazconti, Concepcion
AU - Carroll, Kenneth C.
AU - Brusseau, Mark L.
N1 - Funding Information:
This research was supported by the University of Arizona TRIF Water Sustainability Program through the Center for Environmentally Sustainable Mining, and the NIEHS Superfund Research Program ( P42 ES04940 ). We would like to thank Jody Waugh for his support and assistance. We thank Andy McMillan, Hakan Akyol, Andrew Borden, and Justin Berkompas from the U of A Contaminant Transport Laboratory for their assistance. We thank Dr. Christopher Eastoe of the Environmental Isotope Laboratory at the University of Arizona for sulfur isotope analysis. We thank the reviewers for their constructive comments, which have helped to improve the manuscript.
PY - 2014/8
Y1 - 2014/8
N2 - The impact of electron-donor addition on sulfur dynamics for a groundwater system with low levels of metal contaminants was evaluated with a pilot-scale biostimulation test conducted at a former uranium mining site. Geochemical and stable-isotope data collected before, during, and after the test were analyzed to evaluate the sustainability of sulfate reducing conditions induced by the test, the fate of hydrogen sulfide, and the impact on aqueous geochemical conditions. The results of site characterization activities conducted prior to the test indicated the absence of measurable bacterial sulfate reduction. The injection of an electron donor (ethanol) induced bacterial sulfate reduction, as confirmed by an exponential decrease of sulfate concentration in concert with changes in oxidation-reduction potential, redox species, alkalinity, production of hydrogen sulfide, and fractionation of δ34S-sulfate. High, stoichiometrically-equivalent hydrogen sulfide concentrations were not observed until several months after the start of the test. It is hypothesized that hydrogen sulfide produced from sulfate reduction was initially sequestered in the form of iron sulfides until the exhaustion of readily reducible iron oxides within the sediment. The fractionation of δ34S for sulfate was atypical, wherein the enrichment declined in the latter half of the experiment. It was conjectured that mixing effects associated with the release of sulfate from sulfate minerals associated with the sediments, along with possible sulfide re-oxidation contributed to this behavior. The results of this study illustrate the biogeochemical complexity that is associated with in-situ biostimulation processes involving bacterial sulfate reduction.
AB - The impact of electron-donor addition on sulfur dynamics for a groundwater system with low levels of metal contaminants was evaluated with a pilot-scale biostimulation test conducted at a former uranium mining site. Geochemical and stable-isotope data collected before, during, and after the test were analyzed to evaluate the sustainability of sulfate reducing conditions induced by the test, the fate of hydrogen sulfide, and the impact on aqueous geochemical conditions. The results of site characterization activities conducted prior to the test indicated the absence of measurable bacterial sulfate reduction. The injection of an electron donor (ethanol) induced bacterial sulfate reduction, as confirmed by an exponential decrease of sulfate concentration in concert with changes in oxidation-reduction potential, redox species, alkalinity, production of hydrogen sulfide, and fractionation of δ34S-sulfate. High, stoichiometrically-equivalent hydrogen sulfide concentrations were not observed until several months after the start of the test. It is hypothesized that hydrogen sulfide produced from sulfate reduction was initially sequestered in the form of iron sulfides until the exhaustion of readily reducible iron oxides within the sediment. The fractionation of δ34S for sulfate was atypical, wherein the enrichment declined in the latter half of the experiment. It was conjectured that mixing effects associated with the release of sulfate from sulfate minerals associated with the sediments, along with possible sulfide re-oxidation contributed to this behavior. The results of this study illustrate the biogeochemical complexity that is associated with in-situ biostimulation processes involving bacterial sulfate reduction.
KW - Iron sulfide precipitation
KW - Isotopic fractionation
KW - Stable isotopes
KW - Sulfate mineral dissolution
KW - Sulfate reduction
KW - Sulfide re-oxidation
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U2 - 10.1016/j.jconhyd.2014.06.010
DO - 10.1016/j.jconhyd.2014.06.010
M3 - Article
C2 - 25016586
AN - SCOPUS:84904352659
SN - 0169-7722
VL - 164
SP - 240
EP - 250
JO - Journal of Contaminant Hydrology
JF - Journal of Contaminant Hydrology
ER -